Rotary air drier



April 25, 1944. Lu-rz ROTARY AIR DRIER Filed Feb. 17, 1942 2 Sheets-Sheet l INVENTOR DW/V/EL L April 25, 1944.

D. H. LUTZ ROTARY AIR DRIER Filed Feb. 17, 1942 2 sheets sheet 2 IINV'ENTOR ZDH/V/EZ H LUTZ TORNEY Patented Apr. 25, 1944 UNITED STATES PATENT OFFICE 2,347,356 ROTARY AIR DRIER Application February 17, 1942, Serial No. 431,183

2 Claims.

The present invention relates to air driers, and, more particularly, to natural air driers of the rotary type in which the drying medium is natural air of a temperature substantially equaling the temperature of the atmosphere surrounding the drying machine.

As those skilled in the art know, heretofore, a great variety of drying machines was in use for the purpose of drying and dehydrating foods, including the various kinds of fruits and vegetables. In most of these machines preheated air of relatively high temperature was employed as the drying medium, and such preheated air was passed in contact with the materials to be dehydrated by means of fans or similar devices. In order to assure good heat-exchange between the drying medium and the materials to be dried, the materials were comminuted and spread out on a plurality of parallel-spaced trays or screens. The principal difiiculty in the operation of such conventional machines resided in the proper control of the drying or dehydrating temperature. When the temperature of the drying air was too low, a very long time was needed for carrying out the process of dehydration, while when the temperature of the drying air was too high, the cellular structure of the materials was ruptured due to the extremely quick withdrawal of moisture therefrom and an inferior product was obtained.

It was already suggested to avoid the difficulties encountered in drying and dehydrating certain products, particularly liquids, and semi-liquids, by means of a machine in which a central stationary support or receptacle was provided for the material to be acted upon, in combination with air-scooping means arranged to rotate independently on the central support while maintaining such a relation to said support as to cause a current of drying air of room temperature to pass through the same. While machines of the described character avoided the danger of overheating the materials to be dehydrated, they were rather bulky and cumbersome in their structure. Particularly, serious problems of constructions were present in the design and operation of these machines in view of the stationary support or receptacle for the material to be dehydrated which had to be connected in a substantially gas-tight manner with the rotary air scoops of relatively large dimensions. As a consequence of these difiiculties none of the driers based on this natural air drying principle became of any importance in the drying and dehydrating art. Although also various other suggestions and proposals were made to solve the outstanding problem and to provide the art with a completely satisfactory natural air drier, none, as far as I am aware, of these suggestions and proposals was completely satisfactory and successful on a practical and industrial scale.

I have discovered that the problem may be solved in a remarkably simple manner.

It is an object of the present invention to provide a drier or dehydrator of novel and improved character which completely eliminates the difilculties encountered in the construction and operation of conventional machines.

It is another object of the present invention to provide a natural air drier which may be employed for the dehydration of all kinds of fruits and vegetables in a quick; efiicient and convenient manner without resorting to the use of a preheated gaseous drying medium.

It is a further object of the present invention to provide a natural air drier in which a central, rotary support for the materials to be dehydrated is employed in combination with rotary air scooping means, means being provided for accurate control of the velocity of the air currents, the speed of rotation and of the air inlet and outlet ports in order to correctly adjust the operating conditions to the character of the material to be dehydrated.

The invention also contemplates a rotary air drier which is simple in construction, quick and eflicient in its operation, and which may be readily manufactured and operated on a practical and industrial scale at a low cost.

Other and further objects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, in which:

Fig. 1 illustrates a top plan view of a preferred embodiment of the invention, with parts of the casing broken away for the sake of clarity;

Fig. 2 depicts a side elevational View, somewhat fragmentary in character, of a portion of the lower part of the drier shown in. Fig. 1, including a portion of the casing and of the platform upon which the casing revolves;

Fig. 3 shows a horizontal sectional view of the drier casing with the supporting trays stacked therein and with the side doors partly opened;

Fig. 4 is a perspective View of the drier casing with trays stacked in one section thereof;

Fig. 5 is a horizontal sectional View, somewhat fragmentary, of one of the end portions of the casing; and

Fig. 6 is a sectional detail View of a portion of the trays for holding the materials to be hydrated.

Broadly stated, according to the principles of the present invention, I provide a platform or base upon which is mounted a rotary casing. Partition walls separate this casing into a pair of individual parallel compartments in each of which means are provided for holding a plurality of spaced trays arranged in superimposed stacked relation for holding the material to be dehydrated which thus are rotated together with the casing. Each of the compartments is of an elongated shape With air scooping means at one end and with air outlet means at the other end. The dimensions of the trays are closely conforming to the inner dimensions of the compartments so that the air streams set up during rotation of the casing are forced through the trays and through the materials thereon, thereby exerting a powerful drying and dehydrating action. I have found that during rotation of the casing and of the associated air scooping means a pressure differential develops between the inlet and the outlet openings. This pressure differential is due to the pressure of the air forced into the casing by the air scooping means and to the negative pressure of the air ejected from the casing by the centrifugal force. Whether the pressure prevailing in the casing is above or below atmospheric pressure, largely depends on the circumstance Whether the effect of the air scooping means or of the centrifugal force is the stronger. The relative value of these forces and of the resulting pressure may be readily adjusted by controlling the speed of rotation of th casing and by adjusting the inlet and the outlet openings of the casing. In this manner, the operating conditions may be easily and accurately adjusted to the character of a large variety of materials to be dehydrated. Generally speaking, a partial vacuum, or sub-atmospheric pressure within the casing is a decided advantage since the removal of moisture from the materials to be dried increases with the decrease in pressure, as those skilled in the art will readily appreciate.

The invention will now be more fully described to those skilled in the art with erence to the drawings.

In the preferred form of my invention illustrated in the drawings, a rotatable casing l is provided having agenerally elongated shape and comprising top and bottom walls 2 and 3, outer side walls 4 and 5, and a central wall or partition 6 dividing the central portion of the casing into a pair of parallel compartments or chambers I and 8. These compartments have means incorporated therein for carrying trays 9 in the center portion thereof, containing the materials to be dried, dehydrated, or evaporated. The trays are preferably elongated in form and are constituted of a light wooden frame I with their bottom formed of fine wire mesh screen II. To the upper side end portions of the frames are secured spacing blocks l2 so that when the trays are stacked in superimposed relation, an air space or channel is provided between the individual trays for permitting currents of air to readily pass above and below the trays and through the materials to be dehydrated. This particular form of construction will be best observed in Figs, 3 and 4 of the drawings.

To reduce the resistance of air striking the end walls of the trays during the operation of the drier,'the inlet end walls of the trays are tapered to an edge or line !3 (Fig. 6) to freely direct the currents of air above and below the trays without introducing any appreciable resistance against the free flow of the air currents.

Carried by the bottom, top and outer side walls of the casing are scoops I4 and I5 which are curved in opposite directions, as shown in particular refthe entrance surfaces [6 and l! of compartments 7 and 8. It is preferred to form these scoops integrally with the Walls of the casing although, of course, they may be individual and separate structural elements secured to the casing proper by means of bolts, rivets, or spot welding.

To provide adjustment for the amount of air entering the compartments, the ends of partition 6, adjacent the scoops, are provided with adjustable panels I8 which extend from the bottom to the top of the casing. The adjustment of the panels may be obtained by means of set screws I9 mounted on the ends of partition 6 and passing through horizontal slots formed Figs. 1, 3 and 4, to, form air scooping means at 75 in the wall of the panels, as shown in Figs. 3 and 5. In the loosened condition of set screws l9, panels I8 may be readily adjusted into any desired position and may be fixed in such position by tightening set screws [9. Similar means may be provided for regulating the flow of air at the discharge ends of compartments 1 and 8 and are denoted by reference characters 20 and 2!, in Figs. 3 and 5. In view of the similarity of construction, their operation and their structure will be readily understood by those skilled in the art without any detaileddescription.

Openings 25 are provided in the outer side Walls of the casing through which trays 9 containing the materials to be dehydrated may be readily introduced into-compartments land 8 and may be readily removed therefrom after the dehydration process has been finished. During the operation of the machine, these openings are closed by means of doors 25 connected to the outer sides of the casing walls by means of hinges 21, suitable locking means 28 being provided for securing the doors in the closed position.

The drier casing is rotatably mounted on'a substantial platform or base 3!), as shown in Figs. 1 and 2. To the bottom wall of the easing is secured a circular metal track 3| which is adapted to rest upon rollers 32 and 33 mounted for rotation on platform 36. In the illustrated embodiment of the invention 4 rollers are shown, two of which are arranged in opposed position to form idler rollers 32 and the other two of which are likewise arranged in opposed position to provide drive rollers 33 for imparting rotation to the casing, when desired. The drive r'ollers 33 are mounted on the inner ends of stud shafts 34 secured in bearings 35 and tothe outer ends of the shafts are mounted drive pulleys 36 arranged to be driven by drive belts 3! and 38. To the opposite side of the platform is secured a main drive shaft 39 mounted in bearings 40 and provided with drive pulleys 4| for driving the belts 31 and 38 and rotating the casing at the desired rate of speed.

The driving power for rotating the casing is supplied by an electromotor 42 mounted on platform 38. Electromotor 42 drives a pulley 43 mounted on the outer end of the main drive shaft 39 (Fig. 1). For. the purpose of controlling the speed of revolution of the casing, a variable ratio transmission gear M is interposed be.- tween the electromotor and the main drive shaft. The transmission ratio may be adjusted continuously or in steps by the displacement of control lever 45. In view of the fact that such variable ratio transmission devices are well known to those skilled in the art and do not form part of the present invention, no detailed description thereof will be necessary. I f

From the foregoing description the operation of my improved natural air drier will be readily understood by those skilled in the art. When it is desired to operate the machine, doors 26 are opened and the trays bearing the materials to be dehydrated are introduced into compartments I and -8. Hereafter, the doors are closed and locked by locking means 28. It is advisable to so adjust the amount of materials to be dehydrated on the various trays that the weight of the material in compartment 1 substantially equals that of the material in compartment 8 in order to avoid unbalance which would greatly increase the power requirements. The driving means in cluding electromotor 42 are now energized and the ratio of the transmission gear M is adjusted in accordance with the desired speed required for dehydrating the particular material contemplated. The air inlet openings and the air outlet openings of the compartments are likewise adjusted to the values which have been found best for the material under treatment. During rotation of the compartments and of the air scooping means air currents are set up through the compartments and in view of the fact that the stacks of trays practically completely fill out the compartments, substantially all of these air currents are utilized for the process of dehydration whereby very great efficiency of operation and relatively high drying speeds are obtained. I have found that my natural air drier in which the material to be dehydrated rotates together with the air scooping means provides results greatly superior to the results obtainable by means of prior natural air driers in which the material to be dehydrated is in a stationary position. While the reason for this interesting phenomenon is not completely clear, it is possible that this considerably higher efficiency is at least partially due to the circumstance that in the device of the invention the air currents set up by the air scooping means are practically fully utilized for the process of dehydration while in the prior devices in which the materials to be dehydrated are stationary and only the air scooping means are rotated, a substantial portion of the air currents are lost due to the unavoidable air leakage between the stationary and the rotary portions of the machine. A further important advantage of my novel natural air drier is that during rotation of the trays carrying the materials to be dehydrated, the individual particles of the material are subjected to certain mechanical forces which may cause continuous rearrangement of such particles with respect to each other. Therefore, during the process of dehydration, always new portions of the materials will be exposed to the drying air current whereby the speed and the overall efficiency of the dehydration is greatly increased.

In order that those skilled in the art may have a better understanding of the invention, the following table is given which indicates the water content and the approximate drying time and speed for various vegetables and fruits.

Fruits Water content Revolutions Per cent n-u-umore:

Although the present invention has been described in connection with a preferred embodiment thereof, variations and modifications may be resorted to by those skilled in the art without departing from the principles of the present invention. I consider all of these variations and modifications as within the true spirit and scope of the present invention, as disclosed in the foregoing description and defined by the appended claims.

I claim:

1. A natural air drier comprising a rotatable casing having a pair of parallel chambers for the reception of the material to be dried, the chambers each having one end thereof formed to provide an air scoop and having their other ends fully open to provide air outlets, the air scoop of each chamber extending radially beyond the open end of the other chamber and having its open, or air intake, side facing the direction of rotation of the casing, means for varying the size of the air intakes of the air scoops, panels carried by the air chambers at the outlet ends of the chambers for adjustment inwardly or outwardly of said ends to regulate the discharge of air from the chambers, means for securing the panels in adjusted position, trays arranged one above the other in the chambers for supporting the material to be dried, means spacing the trays to provide air channels between the same, the trays including frames having bars extending across the chambers in 'facing relation to the scoops, said bars having the upper and lower sides of their front portions beveled to direct the air into the channels and provide for the free flowing of the air through the chambers, and means for rotating the casing.

2. A natural air drier comprising a rotatable casing having a pair of parallel chambers for the reception of the material to be dried, the chambers each having inner and outer side walls and top and bottom walls and having one end thereof formed to provide an air scoop and having the other end thereof fully open to provide an air outlet, the air scoop of one chamber ex tending radially beyond the open end of the chamber and having its open, or air intake, side facing the direction of rotation of the casing, panels mounted on the inner side walls at the outlet ends of the chambers for adjustment inwardly or outwardly of the chambers and across the air intakes of the scoops to vary the effective size of the intakes, panels carried by the outer side walls and by the top and bottom walls at the outlet ends of the chambers for inward or outward adjustment independently of each other and said first panel to vary the effective length of the chambers and thus regulate the passage of the air from the chambers, means for securing the panels in adjusted position and means for rotating the casing.

DANIEL H. LUTZ. 

